1. Field of the Invention
The present invention relates to a memory device control system for accessing a memory device that has a plurality of data areas each control method of which is different.
2. Description of the Related Art
In the prior art, since all areas of one memory device are operated by the same control method, one file system was provided. In such memory device, even in such a environment that two tasks or more that are going to execute the access process can be operated in parallel, it was a normal method that, since only one file system is provided, the mediating process applied to access one memory device in parallel was carried out by this one file system.
Here, in the memory device such as the hard disk, etc., the “file system” means such a system that manages the information indicating what files are stored in which locations of the memory device. In the file system, the methods of making files or directories in the memory device, the data recording system, locations of the management area, the application method, etc. are decided. As the typical file system, there are FAT, NTFS, etc.
Meanwhile, in recent years, the memory device having a plurality of data areas the control method of which is different respectively are employed. For example, when the memory device such as the memory card, or the like is employed in the built-in device, the secured data areas and the unsecured data areas, to which different control methods are applied respectively, are provided to the memory card in order to attain the security reinforcement of the memory card.
Since the control methods are different in the secured data areas and the unsecured data areas, two types of file systems must be used to implement the access process applied to the memory card. In this manner, in order to access to the memory device having a plurality of data areas the control method of which is different respectively, the file systems that are different mutually must be prepared every different data area respectively to execute the access process.
As the technique for accessing to one memory device from two types or more of file systems, there is the file management system that is able to absorb differences in different file systems (see JP-A-9-128277). According to this system, differences are absorbed by converting file accesses, which have different protocols of plural OS's, into the protocol of the particular OS.
However, according to the technique set forth in Patent Literature 1, for example, when a plurality of tasks are going to access one memory device in which a plurality of data areas having the different control method cannot be accessed simultaneously, the mediation that takes account of all the access requests issued to a plurality of files system must be carried out. Therefore, such mediation must be carried out at a task level.
When a plurality of tasks are operated in parallel and different data areas are accessed simultaneously via a plurality of file systems, other tasks cannot access other data areas at all based on the mediation at a task level during when one task is being to access the data area Actually, when the mediation at a task level is carried out, the processing unit used to access the memory device depends on the file system, and thus it is not feasible to operate a plurality of tasks in parallel by using the different file systems. As a result, it was impossible to operate a plurality of tasks simultaneously by using the data stored in different data areas.
For instance, in the multitask system, when the music file in which the media player task is stored in the secured data area of the memory card is read on occasion to output the music, the music output is carried out as one task. Therefore, such a problem existed that the file viewer task cannot display contents of the text file, which is stored in the unsecured data area of the memory card, during the playing of the music.